gas fired furnace won't turn on

i have a residential gas fired induced draft furnace that wont start.I've tried all the steps in the manual?When I take the fuse out the blower starts working.When I put the fuse back in and try to start no reaction at all.Plus, I can find no manual reset auxiliary swith on top of blower any advise please?

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Not enough information. Give us a brand, model if possible, whether it is an upflow, in other words is the blower on the bottom and the air goes up through, a downflow, blower on top, air goes down through or horizontal mount. Are you taking the fuse out of the control board? Do you have a test meter or test light? Do the basics, check the thermostat, is it switched to heat? Is it adjusted high enough to call for heat? With the cover off, the power should be off if the safety interlock switch is working properly, otherwise switch it off. Set your meter to read in the 24 volt range, your test light should be capable of this also. Put the test leads across the R and W terminals. While holding the leads on the terminals energize the furnace. You might need an assistant to help with this. If there is a call for heat you should get a zero volt reading or no light. This is not conclusive. Turn it off. Now put the leads on the R and C terminals and power up again. Now you should get a light or a voltage reading in the 24 volt range. Turn off. Now put the test leads on the W and C Terminals. Power up. You should again get a 24 volt reading. If so, you have a call for heat, the problem lies elsewhere. Next culprit is the draft inducer. Does it start after a maximum 10 - 15 second delay? Does it hum but not start? Does it get hot? Bad motor or a blockage in the inducer blower. Pull it out of the housing and check for debris inside. Try to spin the wheel. Stuck? Bite the bullet and replace it. They have gone way up in price the last few years but trying to fix is almost hopeless. You might be able to free it up but chances are it will fail shortly. If it was fall going into winter I would say give it a try but it is spring coming out of winter and its highest usage. The bearings are likely failing. Start there, good luck. Beyond that you might want to call in a certified technician, NO brother-in-laws!!